1. Field of the Invention
The present invention relates generally to an underground mine roof support for supporting the roof, and, more particularly, to a yieldable mine roof support that allows for adjustment of the overall length of the mine roof support to fit between a roof and a floor of a mine entry.
2. Description of the Related Art
Over the past several years, Burred Mining Products, Inc. of New Kensington, Pa. has successfully marketed and sold a mine roof support product sold under the trademark THE CAN®. THE CAN support is comprised of an elongate metal shell that is filled with aerated concrete. The use of aerated concrete in THE CAN support allows the support to yield axially in a controlled manner that prevents sudden collapse or sagging of the mine roof and floor heaving. THE CAN support yields axially as the aerated concrete within the product is crushed and maintains support of a load as it yields.
A typical size of THE CAN support is approximately six feet (1.8 meters) in height and two feet (0.6 meters) in diameter. The overall height of THE CAN supports is based on the average size of the mine entry with each support being of a height that is less than an average height of the mine entry in which the supports are to be installed. In order to install each support, wood planks (or other appropriate cribbing materials such as aerated concrete blocks) are placed beneath THE CAN support to level the support and additional wood planks or other cribbing materials are placed on top of the support until the space between the support and the roof is filled. Essentially, the cribbing materials are tightly wedged between the support and the roof so as to cause each THE CAN support to bear a load of the roof upon installation. Even though these cribbing materials can be installed by mine personnel in a manner that ensures that each support begins bearing a load of the mine roof upon installation, there still exists a need in the industry to provide a mine roof support that is capable of being installed in a manner that substantially fills the space between the mine roof and the mine floor without requiring the installation of cribbing materials above the roof support. In addition, even though cribbing materials may be tightly inserted between the top of the mine roof support and the roof of the mine, there is still an amount of movement of the mine roof relative to the mine floor (or vise versa in the case of floor heaving) that can occur before the mine roof support is able to fully bear the load. Thus, there still exists a need in the art to provide a mine roof support that is capable of bearing a load of the mine roof support shortly after installation but before the roof begins converging toward the floor or vise versa.
Thus, it would be advantageous to provide a mine roof support that is installable within a mine entry that substantially fully extends between the mine roof and the mine floor when properly installed. It would be a further advantage to provide a mine roof support that is installable within a mine entry that is capable of bearing a load of the mine roof shortly after installation without the need of cribbing materials placed above the support in order to decrease installation time and to increase the initial load bearing capacity of the mine roof support.
These and other advantages will become apparent from a reading of the following summary of the invention and description of the illustrated embodiments in accordance with the principles of the present invention.